INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 6, ISSUE 03, MARCH 2017
ISSN 2277-8616
Resins In The Heavy Organics Precipitate From
Crude Oil With Single N-Alkane And Binary
Mixture N-Alkane Solvents
Mfon. C. Utin, Samuel. E. Ofodile, Regina. E. Ogali and O. Achugasim
ABSTRACT: Heavy organics from crude oil was precipitated using single n-alkane and binary mixtures of n-alkane solvent of varying ratios.
Precipitation can occur due to changes in composition, temperature or pressure during crude oil production and transportation. The heavy organics
Precipitates were studied and fractionated using column chromatography to separate them into different components. The focus of this research is to
determine the resin content of the solid precipitate from the various ratios of the different binary mixtures using uv-visible spectroscopy. The results
obtained showed increase in the absorbance of the resin content with decreasing carbon numbers for both single nC 5, nC6, nC7 and binary mixtures
(3:1) of nC5: nC6, ( 3:1) of nC5:nC7and (3:1) of nC6: nC7.
KEYWORDS: Absorbance,Binary mixture,Heavy organics, n-alkane, Resin.
————————————————————
INTRODUCTION
Mechanical and chemical cleaning methods are employed
to maintain production, transportation and processing of
petroleum at or close to economical level. Due to various
factors, precipitation, flocculation and deposition of heavy
organicsoccur. The major interest in the oil industry is when
and how much heavy organics will precipitate, flocculate
and deposit under operating conditions. Laboratory and
field data have proven that heavy organic substances in the
oil consist of particles with molecular weights from one
thousands to several hundred thousand [1],[ 2]. Crude oil at
atmospheric pressure and ambient temperature contains
three main fractions mainly oils (saturate and aromatic),
resin and asphaltenes [3]. Resins are fractions soluble in
light alkanes like pentane and heptane but insoluble in
liquid propane [6], [7], [8]. Resins are fraction of
deasphalted oil that is strongly adsorbed in surface-active
materials such as fuller’s earth, alumina or silica and can
only be desorbed by a solvent such as pyridine or a mixture
of toluene and methanol. They have several functional
groups including ketones, acid, ester, hydroxyl, nitrogen
and sulfur-oxygen. Resins are a solubility classthat overlap
both to the aromatic and asphaltene fraction and little work
has been reported on its characteristics compared to
aspaltenes. Since asphaltene and resin form the most polar
fraction of crude oil, resin have a strong tendency to
associate with asphaltene and such association determines
to a large extent their solubility in crude oil [2], [9], [10].
They are the very aromatic component and their structure is
not well defined. They are polar, polynuclear molecules
consisting of condensed aromatic rings, aliphatic side
chains and few heteroatoms. Asphaltenes are fractions
separated from crude oil or petroleum products upon
addition of light hydrocarbon solvent such as n-heptane.
_________________________
 Mfon. C. Utin, Samuel. E. Ofodile, Regina. E. Ogali and
O. Achugasim
 Department of Pure and Industrial Chemistry, University
of Port Harcourt PMB 5323, Choba Port Harcourt, Rivers
state [email protected]
They are solid particles which are suspended colloidally in
crude oil and are stabilized by large resin molecules.
Asphaltene precipitation is a complex phenomenon that
involves asphaltene and resins. [1], [6] .During production
of crude, water/ oil emulsions are formed. They are
stabilized by asphaltenes and resins which are colloidally
dispersed in the crude oil [4]. Resins are one of the crude
oil constituents that have impact on petroleum refining
operation. Crude oil stability is dependent upon the
molecular relationships of asphaltene and resin constituents
and the balance with the other constituents of petroleum [5].
Since crude oil is a continuum of several thousands of
molecules, it is very difficult todefine a cut off between
asphaltene, resin and oils. The variables introduced in each
method may generate different fractions of asphaltene with
different methods. Like asphaltene, resins are defined
according to the solvents used for their separation. In
chromatograghic elution, discrepancies in the amount and
chemical composition can be found if adsorbents are
different or elution time is varied [11]. Direct current (DC)
conductivity studies showed that resins are unlikely to coat
asphaltene nanoaggreagates in anhydrous organic solvents
and Nellensteyan hypothetical model of resin adsorbed on
asphaltenes to provide a steric stabilizing layer is not valid
[12]. However the roles of resin on asphaltene adsorption at
the solvent/ water interface becomes important when in the
presence of water or a solvent, thus providing resin and
natural surfactants to diffuse first to the interface before
being replaced by asphaltene [13]. The amount of adsorbed
asphaltene on water equally depends on the resin to
asphaltene ratio [3], [14]. The molecular weight distribution
of nC5,nC7 and nC9asphaltene fraction was reported with
expectation of three different molecular weight distribution
of asphaltene. The molecular weight distributions will
depend on the level of interactions among asphaltene, resin
and co-precipitated high molecular weight paraffin. When npentane was used high molecular weight paraffin coprecipitated with the asphaltene and resin. The resin
contents of the precipitate for different precipitating solvents
increases as the number of carbon atoms in the
precipitating solvent decreases [15]. The fact that
asphaltenes, resins, diamondoids, waxes or high molecular
weight paraffin etc can be precipitated makes it safer to
refer to the precipitate simply as heavy organics precipitate.
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INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 6, ISSUE 03, MARCH 2017
It becomes expedient to show if this heavy organic
precipitate which consist of mainly asphaltenes also
contains some percentage of resin using single n-alkane
and binary n-alkane mixtures. The contributions by the
different compound types to this variation had never been
studied. The aim of this research therefore is to determine
the resin content of the precipitate obtained from both
single n-alkane and binary mixtures of n-alkanes solvents at
various ratios.
ISSN 2277-8616
RESULT AND DISCUSSION
The results obtained are shown in table 1 and the figures
below
TABLE 1: Absorbance of Resin from Heavy Organics
Precipitation using different mixtures of n-alkanes Solvent
PRECIPITANTS
Vol.Ratio
C5&C6
C5&C7
C6&C7
METHODOLOGY
0:1
Crude oil used for this research was obtained from NNPC
research and development laboratory, Port Harcourt, Rivers
State, Nigeria. The reduced crude oil was obtained by
removing the distillate at 2600C using atmospheric
distillation. Precipitation of heavy organics was carried out
using both the single n-alkane and binary n-alkane mixtures
of different ratios. 30mlof each of the single solvents
(pentane, hexane and heptane) and 30ml of each of the
binary mixtures (C5:C6, C5:C7 and C6:C7) of varying ratios
were added to 1g of the oil in the appropriate flasks. The
mixtures were mechanically shaken for 30minutes and kept
for 48hrs before filtration. Each of the solutions obtained
after precipitation was filtered using vacuum filtration
system with 0.45nm membrane filter to separate the solid
precipitate from the filtrate. The solid precipitate was dried
in an oven, weighed and kept in a dessicator for further
analysis. Solid precipitates obtained from the precipitation
process using single n-alkane and binary n-alkane mixtures
of were removed from the membrane filter using
tetrachloroethylene and kept in their appropriate flask. 0.5g
of the precipitate was dissolved in tetrachloroethylene and
introduced into a column packed with silica gel with a
syringe, for saturate, aromatic, resin and asphaltene
(SARA) analysis, affording different fractions from the
column. The saturate (aliphatic) fraction was eluted with
50ml hexane, while 70ml of 1:1 dichloromethane/ hexane
was used for the elution of the aromatic fraction. A mixture
of (1:2, 60ml) of methanol/dichromethane was used to elute
the resin. Elution of the different fractions was monitored
using a uv-visible spectroscope. The resin fraction was
scanned at several wave lengths using uv-visible
spectroscope and absorption at 450nm was selected. Each
of the fractions of resin obtained from the SARA analysis
was measured. The scheme below summaries the methods
adopted for this work.
1:0
2.17
2.17
1.567
1:1
2.041
1.796
1.008
1:2
2.041
0.644
0.35
2:1
2.116
0.825
0.551
1:3
2.089
0.711
0.373
3:1
2.117
2.082
1.42
1.567
0.324
0.324
FIGURE 1: Absorbances of Resin in Solid Precipitate from
different Ratios of (C5:C6) Binary Mixtures of n-Alkane
FIGURE 2: Absorbance of Resin in Solid Precipitate from
Varying Ratios of (C5:C7) Binary Mixtures of n-Alkane
Scheme 1: Chromatographic separation of n-alkane
Precipitate from Crude Oil.
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INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 6, ISSUE 03, MARCH 2017
ISSN 2277-8616
solvent resulting in the decrease. in the amount of resin
/asphaltene precipitated..
REFERENCES
[1] Ashoori S. Mechanisms of Asphaltene Deposition
in Porous Media, A Thesis submitted in partial
fulfilment of the requirements for the degree of
Doctor of Philosophy, School of Engineering,
University of Survey, (2005).
[2] Asok K. Tharanivasan Aspahaltene Precipitation
from Crude Oil Blends, Conventional Oils and Oils
with Emulisified Water, A Thesis submitted to the
faculty of Graduate studies in partial fulfilment of
the requirements for the degree of Doctor of
Philosophy, Department of Chemical and
Petroleum Engineering, Calgary, Alberta, (2012).
FIGURE 3: Absorbance of Resin in Solid Precipitate from
Varying Ratios of (C6:C7) Binary Mixtures of n-Alkane
The results of the resin content of precipitates obtained with
single n-alkane and binary n-alkane mixtures of various
ratios are shown in figure 1, 2, 3 and table 1.The result
shows that the highest absorbance (highest quantity) was
recorded in single pentane (nC5) solvent precipitate in
figure1 followed by nC6 in figure 3 while the least amount
was observed in single n- heptane (nC7) infigure 3. In figure
1, the result for the binary mixture (C5:C6) shows that the
ratio with the higher volume of the lower carbon number
recorded the highest amount of resin in the precipitates
compared to lower volume of a higher carbon number. For
the binary mixture of nC5:nC7 in figure 2 and that of nC6:nC7
in figure 3, the same trend of the result observed. From the
above results, it was observed that the C5:C6 binary mixture
recorded the highest absorbance (highest resin content)
and the least absorbance was shown in C6:C7. The results
for the resins in single solvent precipitates in figure 1, 2, 3
and table 1 equally follows the same trend observed with
the single solvent precipitates in heavy organics. The result
of this work supports a previous report that resin content in
precipitates increases as the number of carbon in the
precipitating solvent decreases [15]. It was equally
observed that the precipitates obtained from heavy organic
precipitation from crude oil using both single n-alkane and
binary n-alkane mixture of various ratio showed increase in
the precipitate with decreasing carbon numbers (16,17). It
has been reported that the phase envelope of heavy
organics precipitate with binary mixture with more of the
lower carbon number recorded a larger envelopes
compared to phase envelopes with higher carbon number
and equally concluded that the phase envelope gives a
qualitative evidence of the asphaltene and resin content of
crude oil precipitates [18].
CONCLUSION
Total heavy organics precipitates consist of different
compound type saturate, aromatic resin and asphaltene.
Quantity of total heavy organics precipitate varies with the
number of carbon atoms in the precipitating n-alkane
solvent. Asphaltene content follow the same trend as the
total heavy organic. From this research it has been proven
that the resins in total heavy organics obtained from both
single and binary mixture n-alkanes solvent of various ratios
follows the same trend of increase in carbon number of
[3] Lamia Goual. Petroleum Asphaltene. University of
Wyoming USA (www.intechnopen.com),(2012).
[4] P. C Schorling, D. G kessel and I Rahimian,
Influence of the Crude Oil resin/ asphaltene ratio
on the Stability of oil/ Water Emulsions,(1999).
[5] D. Mason Part 10: Resins and Polymers in Crude
Oil Refining, (2016).
[6] J.G Speight, The Chemistry & Technology of
Petroleum, Marcel Dekker, New York,(1999).
[7] E.Y. Sheuand O.C. Mullins,
‘’Asphaltenes:
Fundamentals and Applications’’, New York,
Plenum Press,(1995).
[8] S.I Andersen and J.G Speight, Petroleum Resin:
Separation, character and Role in Petroleum,
Petroleum Science and Technology,19(1&2) pp 134, (2001).
[9] J.A Koots and J.G Speight, Relation of Petroleum
Resins to Asphaltenes, Fuel. 54, 179, (1975).
[10] EduardoB.Gonzalez,CalosL.Galeana, Alejandro G.
Villegas andJianzhong Wu, Asphaltene precipitate
in crude oils. Theory and experiments. Al CHE
journal, (2004).
[11] L.
GoualandA. Firoozabadi, Asphaltenes and
Resins Separated from Crude oils,(2002).
[12] F.J. Nellensteyn, The colloidal structure of
Bitumen, in The Science of Petroleum, Vol. 4,
2760, Oxford University Press, London, UK,(1938).
[13] A. Mangual, G. Horvath- Szabo, J.H Masliyah,
Acoustic and Electroacoustic Spectroscopy of
Water –in-Diluted- Bitumen Emulsions. Langmuir,
Vol. 21, No. 19, pp. 8649-8657, (2005).
[14] L. Goual, G.Horvath- Szabo, J.H MasliyahandZ.
Xu, Adsorption of Bituminous Components at Oil –
Water Interfaces Investigated by Quartz Crystal
41
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INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 6, ISSUE 03, MARCH 2017
ISSN 2277-8616
Microbalance: Implications to the Stability of Waterin –Oil Emulsions. Langmuir, Vol. 21, No. 18, pp.
8278-8289, (2006).
[15] D.
Vazquez
and
G.A
Mansoori
(2000). Identification
and
Measurement
of
Petroleum Precipitates. Journal of Petroleum
Science and Engineering. 26, 49-55, (2000).
[16] G. Udourioh; M. Ibezim-Ezeani; and S. Ofodile,
Comparative Investigation Of Heavy Organics
Precipitation from Crude Oil Using Binary Mixtures
and Single N-alkane Organic Solvents. Journal of
Petroleum and Gas Exploration Research 4(4) 5359,(2014).
[17] G. Udourioh; M. Ibezim-Ezeani ; U. Millicent and S.
Ofodile, The Effect of Compositional Changes of
Binary Mixtures of n-alkane Solvents on the
Precipitation of Heavy Organics from a Solution of
Crude Oil Residue, (2015).
[18] M.C. Utin, S.E Ofodile, L.C. Osuji, G.I. Ndukwe and
V.J. Aimikhe, Comparison of the Phase Changes
of Binary Mixtures n-alkanes of Lower Carbon
Numbers, Journal of Applied Chemistry (IOSRJAC) Vol.9, Issue 9, pp132-137, (2016).
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